Recently, we have seen a surprising increase in the use of intranasal cocaine by female cocaine users applying to participate in our cocaine research studies. Little is known about the behavioral and cardiovascular effects of intranasal cocaine in females as compared to males. The objectives of this study are to determine if (1) the effects of intranasal cocaine vary as a function of sex, (2) intranasal cocaine's effects vary as a function of menstrual cycle phase, and (3) the development of acute tolerance (i.e., a diminution of cocaine's effects with repeated dosing in spite of increasing cocaine plasma levels) to the effects of intranasal cocaine varies between males and females, or across the menstrual cycle in females. We will determine a complete cocaine dose response function at two menstual cycle phases in females and at two test occasions in males, with two cocaine doses administered each session. This study will provide data to increase our understanding of the effects of intranasal cocaine in men and women.